Katherine Janeway, who encounters dozens of civilizations as captain of the USS Voyager. She started out as a science officer, so she has great appreciation for science. But I would not want to be stuck in the Delta Quadrant for a period of seven years.

What makes Star Trek good for showcasing science?

Star Trek has been powering along for more than 700 episodes, seven series, and thirteen movies. The mission of the USS Enterprise, the original starship, is to seek out new life. And while it occasionally depicts magical or mystical events, the series is grounded in science.

One concept you wrestle with is how to define life. Why is that so tough, even for biologists?

Think about the characteristics we generally use in defining life as they might correspond with fire. Fire converts matter to energy. And a small spark from a fire can allow a separate fire to emerge— analogous to reproduction. No biologist argues that fire is alive, but there are gray areas elsewhere. Viruses require non-virus host cells for reproduction; they can’t reproduce independently. They don’t generate or store energy. Instead they rely on host cells for energy. So biologists are split on the question of whether viruses are alive or merely natural replicators that capitalize on and influence other living organisms.

How different might extraterrestrial life look from life on Earth?

The universe is filled with the building blocks of life, though the idea of other life forms being recognizable and sentient is a different matter. Life forms on Earth are made from carbon-containing compounds and use water for their biochemical reactions. And all life on Earth evolved from common origins, over almost 4 billion years. The odds that other life forms in the universe would look a lot like us are astronomically improbable. It would require that over a long period of time, the ecosystem, including the climate, would be Earthlike, and it would also ignore chance, which plays a large role.

Several episodes are built on the premise that either life on Earth arose from an alien influence, or life elsewhere arose from Earth. Is either path for life tenable?

The idea that ancient aliens came to Earth and are the ancestors of modern humans isn’t original to Star Trek. But the fossil record tells a different story. If humans arose independently— extraterrestrially or otherwise— then our DNA sequences would not be so similar to those of chimpanzees. Life forms on other worlds may have come from pieces of our planet spewing out, but they are far more likely to be microbial than humanoid. Not only would a life form have to arrive safely on another world; it would also have to find a friendly environment there.

The series plays with genetics and evolution quite a bit. In one episode, aliens that can turn invisible are characterized as the recipients of sophisticated genetic engineering.

The episode gets it right in suggesting that an evolutionary change may stem from a genetic manipulation. Still, the “genetic engineering” here seems devoid of actual genetic change. The alterations seem to have been directly added to their bodies, like giving someone an artificial heart. Changes need to be inherited to be considered evolutionary. The recipient of an artificial heart doesn’t have children who have artificial hearts.

Another episode has someone on the ship accidentally release self-replicating microscopic robots called “nanites.” They “evolve,” cause the ship to malfunction, and eventually learn to communicate with the crew.

Where you have a “genetic disorder” resulting from a mutation, that mutation becomes rarer in the population with each generation, and eventually may be lost altogether. Good mutations become abundant in the population because their bearers, on average, have more children. The process repeats, and the improvements keep building up, potentially even including some change leading to the ability to communicate—assuming such an ability provides an advantage in survival and reproduction. But the episode has the nanites showing a “collective intelligence” and self-awareness. Natural selection doesn’t require that.

By the twentieth-fourth century, are we more likely to evolve into an action-driven Kirk or a super-rational Spock?

I think we’re meant to feel some relationship to both characters. And in the twenty-fourth century, the spectrum of human differences isn’t likely to be very different from today.